Surface treatment of wet felts



July 3, 19 V G. w. THOMAS 3,042,577

SURFACE TREATMENT OF WET FELTS Filed Nov. 10, 1958 IN VENTOR.

660790 Z0. Tbomas BY fla Lwedj-vw,

flifarneys United States Patent Office 3,642,577 Patented July 3, 1962 3,ii t2,577 SURFACE TREATMENT Gi WET FELTS George W. Thomas, Clar net, than, assignor to Wood Conversion (Zompany, St. Paul, Minn, a corporation of Delaware Filed Nov. 1%), 1953, Ser. No. 772,949 lit. Claims. (til. 162-115) The present invention relates generally to the production of specialized surfaces, and in particular to the production of contoured surfaces for decorative or functional purposes.

In the production of waterlaid felts of fibers for drying to rigid boards, fibers in water suspension are felted on a Fourdrinier machine. The slurry charged onto the screen is highly aqueous and levels off to a generally level surface as it is gradually dewatered to a fiber concentration such that when the surface is disturbed, it does not relevel itself, as it does earlier in progress from the original slurry to such state.

Heretofore, it has been known to disturb the surface of such a transient suspension in the case of wood fibers, by mechanically moving localized portions of the top layer, as set forth in the US. Frost Patents No. 2,154,201 and No. 2,178,631.

The present invention is more particularly directed to forming depresisons or elevations or both in a final board, which are more pronounced than the irregularities contemplated in said patents.

In the practice of the said US. patents, the fiber mass must be disturbed at a region having a more or less fixed proportion of water and fibers to maintain a constancy of effect. The disturbance is merely mechanical.

I have discovered that a greater variety of effects may be created by increasing the proportion of water in the mass being disturbed, and this is effected by utilizing a jet of water to effect the disturbance. However, certain disadvantages have been noted in using a stream of water on wet felts already formed or being formed. When the slurry or its felted residue contains an agent which may be flushed out with water drained from the felt, the content of such agent may become locally deficient or absent, to the detriment of quality or character of the board. However, when there is no such agent to be removed, the original felted formation of the residual slurry settling on the screen is disturbed and the fibers loosened from this original formation are more loosely held when the felt is dried to a rigid board. When such a board with the fibers so loosened is reduced to a plane face, as is commonly done by sanding, at least a portion of them are bodily removed. This result is more noticeable when the character of the fibers to form a strong rigid board requires that the mass to be felted include added binder to bond the dried fibers together. Mineral fiber boards usually require added binder. Cellulosic fibers may be felted to a strong board without added binder, by the expedient of hydration to produce the paper-makers bond of hydrated cellulose as part of the fibers.

However, there are frequently other agents incorporated into aqueous slurries to be felted to exercise some function in respect to the finished board, and they may be such that the jet water locally and variously reduces or removes the content thereof. When the mass contains soluble or dispersed material intended to remain with the fibers, such as water-soluble or colloidal, or finely dispersed wax, or rosin, or pigments, or clays, or binders, typical binders being starch in gel or grain form, resin solutions or dispersions, such as soluble thermosetting phenol-aldehyde resin, or latex, one or more of these may be replaced by introducing it with the jet water.

It is, therefore, the object of the present invention mechanically to disturb a wet fiber felt formed by dewatering a slurry of fibers on a screen, by directing onto the surface before drying the wet felt a disturbing jet of water containing one or more added materials to remain in part at least in the felt.

It is an object of the invention to disturb the surface of a wet fiber felt by a jet of water containing one or more agents to replace in function one or more of agents of the original slurry which are subject to removal from the felt by removal of water during or after such disturbance.

In particular, it is an object of the invention to disturb the surface of a wet fiber felt by a jet of water containing binder for the fibers.

Various other and ancillary objects and advantages of the invention will become apparent from the following description and explanation of the invention, as illustrated by the accompanying drawing, in which:

FIG. 1 represents in cross-section a dried mat having a disturbed top surface.

FIGS. 2 and 3 represent the dry board sanded to the levels of lines 22 and 3-3 respectively of FIG. 1.

in the process of the Frost patents, the wet mass being dewatered by drainage or suction or both is mechanically disturbed without change in concentration of solids in the aqueous content. Later, after further dewatering the disturbed felt is pressed between rolls or between screens to express more water. This shifts the wet. mass and levels the irregular surface to an uppermost plane with irregularly located shallow depressions. Then, the felt is ried.

in the present invention, it is preferred for the desirable effects not to press the wet mat after disturbance, thus to form irregularities of greater dimensions in depth. Where an uppermost level is desired in the finished board, it is preferred to achieve it mechanically after drying, as by sanding. Thus, the greater depth is retained.

The fibers may be entirely mineral, or entirely vegetable, or a mixture of the two in any proportion. The material subject to loss or depletion oby the drainage away of jet water, may be hinder, or size, or other ingredient. Binder for example, may be in solution, such as an alkaline solution of phenol-formaldehyde resin, for example, those disclosed in U.S. Booty Patents Nos. 2,462,252 and 2,462,253. The initial binder may be a cooked starch exemplifying a colloidal solution. The binder may be a resin dispersion such as a latex of a polymerized resin. The binder may be a physical suspension, for example, one of uncooked starch grains. Size may be emulsified or dispersed material, such as wax or rosin, to be activated by heat on drying. All of these materials present in water are characterized as distendible, so that they may, to considerable degree, be washed out of the wet felt, and in the case of water-Soluble ones out of a high-density felt as well.

Consequently, when a felt in process of formation, or after the maximum mechanical dewatering by suction and pressing is impinged upon by a stream of water, the water removes the water-distendible content locally at least, regardless of whether the excess water is drawn through the felt or diffuses laterally into the felt.

Where a wet felt so disturbed by a jet of water lacking added content for forming ridges, or valleys, is dried, it has been found that the uppermost regions and the regions bounding depressions, are poorly bound into the board and are easily knocked away, as for example in sanding to a common level.

To overcome this weakness of structure I include in the water for the jet, a suitable conent of binder to remain with the fibers which retain jet water, so that when the felt is dried the surface has adequate overall strength. The binder may be the same as that used in the felt.

In a particular case wherein board is made for cutting 39 to square ceiling tile, I have used the jet to form depressions into the board for enhancing the acoustical properties of the uncoated dry felt, or for imparting acoustical properties to the dry felt which is later coated on its surface surrounding the depressions.

EXAMPLE 1 A slurry is formed containing:

Parts by weight Mineral fiber 90 to 95. Amosite asbestos to 10. Uncooked tapioca starch to 13. Wax-rosin emulsion precipiated on the fibers 1. Water To a consistency of 2 to 4% solids.

That described in Olson U.S. No. 2,754,206.

The slurry is felted on a Fourdrinier screen, and where the fiber consistency is in the range from 45% to 50% by weight of the dewatering felt, the surface is spotted here and there with high-speed spurts of an aqueous dispersion or solution, to form irregularities, or with one or more continuous jets where continuous areas of disruption are desired. The velocity of said jets may be in the range from 6000 to 10,000 feet per minute, but this will vary according to the consistency where applied.

The water may contain suitable binder dispersed therein, such as resin or gelatinized starch of any kind, or any other suitable binder. In the particular instance a jet composition as follows is suitable:

For Resin Percent Water 90 to 95 Resin 10 to 5 For S mrch Water 95 to 97.5 Starch 5 to 2.5

EXAMPLE 2 In the case of vegetable fiber board, such as described in the Frost patents, the slurry may contain:

Parts by weight Wood fiber 100 Size (see Example 1) 2 Water 5000 The jet water for a wet mat deposited from the above slurry may contain from 5 to 10 parts of starch per 100 parts of water, so that its residue of starch is effective to bind the loosened fibers into the undisturbed portion of the felt, when the dewatered felt is dried.

FIG. 1 represents a dried mat 10 of which the mass during formation has been disurbed as described. Tile, for example, of such a board is stacked piece-on-piece, and for that reason the irregular face should have a top level in a plane parallel to the opposite face or back of the tile. As shown in FIG. 1, it has high spots 11 at different levels, which do not permit such stacking.

FIG. 2 represents a board 10* such as that of FIG. 1 with the same contour, with some peaks llll lowered to a plane at such a location that there remain relatively large depressions 13, but also minor peaks id inwardly of plane 12.

FIG. 3 represents the same board of FIG. 1 now designated 10 with the same contour, with more peaks removed by sanding to a new plane 15 such that it defines more plane area in the face of the board and has less area of depressions 16 in that face.

In particular, by control of the jet, a cave-like depression may be made, as shown, at 18 in FIG. 1, with an overhanging ledge 19. This may be so located that it is preserved in the sanding. As shown in FIG. 2, the rem nant 20 of the ledge 10 is retained. Ledges ltl and 20 are examples of a portion which is easily broken away in sanding, when the original binder content has been in part removed or is lacking.

It is to be understood that the invention is not limited to the examples herein given, and that numerous modifications are contemplated as falling within the scope of the appended claims.

I claim:

1. In the method comprising disturbing the formation of a mobile board-forming levelized mass of fiber and Water in process of being dewatered from an aqueous slurry on a felting screen to a wet felt for drying to a rigid board, by directing an aqueous jet onto the levelized surface of the mass in a manner to form irregular depressions and elevations in said surface, said mass containing additive binder for the fibers dispersed in the water and subject to removal from the fibers by dispersion in water passing through the fibers, the improvements wherein said aqueous jet contains binder for the fibers dispersed therein to substitute in function for said first-mentioned binder, whereby on further reduction in water content, substitute binder from the jet remains in the aqueous residue of the jet to function with respect to the fibers washed by said jet.

2. In the method comprising disturbing the formation of a mobile board-forming level-ized mass of fiber and water in process of being dewatered from an aqueous slurry on a felting screen to a wet felt for drying to a rigid board, by directing an aqueous jet onto the levelized surface of the mass in a manner to form irregular depressions and elevations in said surface, said mass containing functional dispersed material as an additive to the fibers subject to removal from the fibers by dispersion in water passing through the fibers, the improvements wherein said aqueous jet contains dispersed therein material to substitute in function for said first-mentioned dispersed material, whereby on further reduction in water content, substitute material from the jet remains in the aqueous residue of the jet to function with respect to the fibers washed by said jet, and drying said felt.

3. The process of claim 2 followed by reducing the top face of the dry mat to a plane bounding the body of the board and located above the bottoms of depressions in said face whereby irregular depressions are present in the resulting plane surface.

4. In the method comprising disturbing the formation of a mobile board-forming levelized mass of fiber and water in process of being dewatered from. an aqueous slurry on a felting screen to a wet felt for drying to a rigid board, by directing an aqueous jet onto the levelized surface of the mass in a manner to form irregular depressions and elevations in said surface, said mass being free of water-dispersed content subject to removal from the fibers by dispersion in Water passing through the fibers, the improvements wherein said aqueous jet contains dispersed binder for the fiber, whereby on further reduction of water content binder from the jet remains in the aqueous residue of the jet to bind the fibers of which the original felted formation has been weakened by said jet.

5. In the method comprising disturbing the formation of a mobile board-forming levelized mass of fiber and water in process of being dewatered from an aqueous slurry on a felting screen to a wet felt for drying to a rigid board, by directing an aqueous jet onto the levelized surface of the mass in a manner to form irregular depressions and elevations in said surface, the improvements wherein said aqueous jet contains dispersed binder for the fiber, whereby on further reduction of water content binder from the jet remains in the aqueous residue of the jet to bind the fibers of which the original felted formation has been weakened by the disturbing jet, and drying the resulting felt to a dry rigid board.

6. The proces of claim 5 followed by reducing the disturbed face of the dry board to a plane bounding the body of the board and located above the bottom of depressions in said face, whereby irregular depressions are present in the resulting plane surface.

7. In the method comprising disturbing the formation of a mobile board-forming levelized mass of fiber and water in process of being dewatered from an aqueous slurry on a felting screen to a wet felt for drying to a rigid board, by directing an aqueous jet onto the levelized surface of the mass in a manner to form irregular depressions and elevations in said surface, said mass containing water-dispersed additive binder subject to removal from the fibers by dispersion in water passing through the fibers, the improvements wherein said aqueous jet contains dispersed binder for the filber, whereby on further reduction of water content binder from the jet remains in the aqueous residue of the mat to bind the fibers washed by said jet, and drying said felt.

8. The proces of claim 7 followed by reducing the top face of the dry mat to a plane bounding the body of the board and located above the bottom of depressions in said rface whereby iregular depressions are present in the resulting plane surface.

9. In the method comprising disturbing the formation of a mobile board-forming levelized mass of fiber predominating in mineral fiber and water in process of being dewatered from an aqueous slurry on a felting screen to a wet felt for drying to a rigid board, by directing an aqueous jet onto the levelized surface of the mass in a manner to form irregular depressions and elevations in said surface, said mass containing water-dispersed additive binder subject to removal from the fibers by dispersion in water pasing through the fibers, the improvements wherein said aqueous jet contains dispersed binder for the fiber, whereby on further reduction of Water content binder from the jet remains in the aqueous residue of the mat to bind the fibers Washed by said jet, and drying said felt.

10. The process of claim 9 followed by reducing the top face of the dry mat to a plane bounding the body of the board and located above the 'bottom of depressions in said face whereby iregular depressions are present in the resulting plane surface.

References Cited in the file of this patent UNITED STATES PATENTS 670,847 Cornell Mar. 26, 1901 995,602 I-Iowes June 20, 1911 2,302,020 Frederick a Nov. 17, 1942 2,373,914 Quinn Apr. 17, 1945 FOREIGN PATENTS 391,952 Germany Mar. 17, 1924 149,416 Great Britain Aug. 10, 1920 

1. IN THE METHOD COMPRISING DISTURBING THE FORMATION OF A MOBILE BOARD-FORMING LEVELIZED MASS OF FIBER AND WATER IN PROCESS OF BEING DEWATERED FROM AN AQUEOUS SLURRY ON A FELTING SCREEN TO A WET FELT FOR DRYING TO A RIGID BOARD, BY DIRECTING AN AQUEOUS JET ONTO THE LEVELIZED SURFACE OF THE MASS IN A MANNER TO FORM IRREGULAR DEPRESSIONS AND ELEVATIONS IN SAID SURFACE, SAID MASS CONTAINING ADDITIVE BINDER FOR THE FIBERS DISPERSED IN THE WATER AND SUBJECT TO REMOVAL FROM THE FIBERS DISPERSED IN THE WATER AND PASSING THROUGH THE FIBERS, THE IMPROVEMENTS WHEREIN SAID AQUEOUS JET CONTAINS BINDER FOR THE FIBERS DISPERSED THEREIN TO SUBSTITUTE IN FUNCTION FOR SAID FIRST-MENTIONED BINDER, WHEREBY ON FURTHER REDUCTION IN WATER CONTENT, SUBSTITUTE BINDER FROM THE JET REMAINS IN THE AQUEOUS RESIDUE TO THE JET TO FUNCTION WITH RESPECT TO THE FIBERS WASHED BY SAID JET. 